Torque motor-driven spool valves are well known in the art including such valves which operate through the utilization of a rotary torque motor having a drive member extending from the rotor thereof into contact with the spool valve to directly reciprocate the spool valve within a bore provided in the valve housing to thereby control the flow of fluid from a source thereof to the load in response to electrical signals applied to the drive motor. Typical of such direct drive servovalves is that illustrated in U.S. Pat. No. 4,793,377 issued Dec. 27, 1988, to Larry E. Haynes et al. The invention described and claimed herein is an improvement over the direct drive servovalve disclosed in U.S. Pat. No. 4,793,377 and therefore the disclosure of U.S. Pat. No. 4,793,377 is incorporated herein by this reference.
The drive motors of such devices include a rotor and stator disposed within a housing in such a manner that the rotor assembly is subjected to the high pressure fluid typically used in servo control systems with which the device is associated. In such devices, it is desirable to have the ability to properly position the rotor to accomplish null centering of the rotor assembly and thereafter to position and clamp the stator relative thereto. Typical of prior art devices of the type described are U.S. Pat. Nos. 4,507,634 and 4,641,812. In each of these devices, the motor housing is utilized as a load carrying structure to clamp the stator in place subsequent to its proper positioning. Furthermore, to retain proper positioning between the stator and rotor assemblies, a locking pin and structural adhesive is utilized as is shown in U.S. Pat. No. 4,507,634. Alternatively, as is shown in U.S. Pat. No. 4,641,812, once the nulling process is completed and the motor stator assembly properly located by index pins, then the outer housing and the motor stator assembly are clamped in place by threading a nut onto a threaded extension of the rotor casing. In either structure, the motor housing becomes a load carrying member for clamping the stator assembly in place. Obviously, such a structure renders it extremely difficult to disassemble such valves for repair and/or maintenance and then reassemble them while maintaining the desired positioning of the stator and rotor assemblies.
It would be desirable in such structures to provide a retainer assembly for securing the stator of the drive motor while retaining the ability to position the stator within a 360.degree. rotational envelope, to securely clamp and lock the stator in the desired rotational position and to eliminate the motor housing cover as the load carrying structure which locks and retains the stator assembly in place.